1. Field of the Invention
This invention relates in general to multi-capsule reed relay assemblies employing a permanent biasing magnet and more particularly to a device for securing the biasing magnet.
2. Description of the Prior Art
Reed contact relays presently known, equipped with a permanent biasing magnet are operated by a coil excited by an opposite polarity to the permanent biasing magnet, which, either makes or breaks the contacts. With these known arrangements the reed contacts and the permanent biasing magnet are accommodated within the exciter coil and are encircled by the coil. Typically, reed contacts and a permanent biasing magnet are inserted individually into the relay and fixed within the coil body. Currently, several methods are employed for fixing or securing the permanent biasing magnet.
One method used, is to secure the permanent magnet by applying epoxy resin cement to the magnet and reed capsules and permanently fixing them to each other as taught by U.S. Pat. Nos. 3,222,758 and 3,237,096. This arrangement has considerable drawbacks because the glass envelopes of the reed capsules and the permanent magnet have different heat expansion coefficients, which, thru excessive heat and humidity as experienced during storage and shipment, cracks the envelopes or adversely effects the adhesive. This causes either the reed contacts to become useless, or through rough handling loosens the magnet. Such changes cause the established values of the permanent magnet to change and consequently, the pull-up and drop values of the reed contacts to the permanent magnet are outside the required tolerances.
Still another method used, is to manufacture the reed capsules and the permanent biasing magnet within a poured resin block as a complete unit, then inserting the block into the coil body as taught by U.S. Pat. No. 3,284,738. The disadvantages to this method are that in an event where one of the reed capsules becomes inoperative the complete unit must be replaced thus discarding the associated components which are operative. Ultimately, this is wasteful of material and labor used to manufacture these units.
Accordingly, it is the object of the present invention to provide a simple, effective, one-piece device for securing the permanent biasing magnet within a multi-capsule reed relay assembly.